"[To] do this to
the right person, to the right extent, at the right time,
with the right motive, and in the right way,
that is not for every one nor is it easy;
wherefore goodness is both rare and laudable and noble."
(Aristotle, Ethics II.9)

The
principle of double effect aims to provide specific
guidelines for determining when it is ethically permissible for a human
being to engage in conduct in pursuit of a good end with full knowledge that the
conduct will
also bring about bad results. Although there has been much substantive
disagreement concerning the precise formulation of this principle, the
principle of double effect generally states that, in cases where an agent contemplates
conduct that has both
good effects and bad effects, the course of conduct selected is ethically
permissible only if it is not wrong in itself and if it does not require
that one directly intend the bad result.

Historically, the
principle of double effect is rooted in the medieval natural law tradition,
especially in the thought of Thomas Aquinas (1225?-1274). For
generations, the principle of double effect was largely confined to
discussions by Roman Catholic moral theologians. But, in recent
decades, the principle has begun to figure prominently in the discussion of
ethicists as well as that of a broad range of contemporary philosophers who are
interested in both ethical theory and applied ethics because this
principle has many applications to ethically complex cases in which an agent
cannot achieve a particular desired good result without also bringing about
some clearly bad result.

Understood in this way,
the principle of double effect "perfects" natural law theory as is evident
in American jurisprudence. While murder is "unnatural" and, hence,
unethical, there are four degrees of murder that can be assigned to such
actions and different punishments are meted out for each degree. Only
first degree murder, which assumes premeditated conduct, merits the death
penalty in some jurisdictions.

The content of the principle of double effect...

Classical formulations of
the principle of double effect require that four conditions be met if the
conduct in question is to be ethically permissible. First: the action
contemplated by the agent be in itself either ethically good or ethically
indifferent (the principle of respect for the agent's autonomy). Second: that the
evil consequence not be directly intended by the agent (the principle of
nonmalfeasance). Third: the good
result not be a direct causal result of the evil result (the principle of
beneficence). Fourth: the good
result must be "proportionate to" the evil result (the principle of
justice).

Of these four conditions,
the first two are general rules of ethics. A human being is never allowed to
engage in ethically bad conduct. Nor may one ever positively will a bad
effect of an action, even though the act would otherwise be lawful.
The classical example involves a censor of books or movies who is allowed to read obscene
literature or preview obscene movies (like a parent deciding about what
books or movies a teenager may read or watch). However, the censor may not
engage in this conduct for the purpose of taking deliberate pleasure in the
unethical thoughts arising
as a consequence of reading the literature or previewing a movie,
although this individual must necessarily permit these thoughts to enter his mind.
The third and fourth conditions, the principles of beneficence and justice, pertain specifically to the principle of the
double effect.

Each of these four conditions
has, however, been a matter of considerable controversy.

The first condition
requires some criterion independent of an evaluation of consequences in
order to determine the ethical character of the proposed action. Objecting
to this requirement are those ethicists who believe that the ethical
character of conduct is exhaustively determined by the nature of its
consequences (e.g., utilitarian ethics).

The second condition
assumes a sharp distinction can be drawn between directly intending a result
and merely foreseeing it. The principle of nonmalfeasance has been the
subject of considerable debate. Some ethicists argue that, if an agent
recognizes a
certain consequence will inevitably follow from a contemplated action then,
in performing the action, the agent must be intending the consequence. Other
ethicists argue, however, that those who defend the principle have failed to delineate any
practicable criterion delineating the "intended" from the "foreseen."
Human beings are not omniscient, these ethicists argue. Defenders typically respond by pointing to the implicit recognition of the
ethical significance of this distinction in the ethical conduct of ordinary
human beings.

The third condition writes
into the principle of double effect the "Pauline principle," that is, "One
should never do evil so that good may come." Reflect, for
example, upon the debate raging about stem cell research. Is the
intentional destruction of a fertilized ovum acceptable because it may
assist researchers to find cures for dreadful and debilitating diseases? Again, ethicists who reject the
view that conduct can have an ethical character independent of its consequences find this condition unacceptable.

The fourth condition
introduces the notion of proportionality into deliberation which, many ethicists
believe, undercuts the ethical absolutism presupposed by the first condition. Although
the first three conditions have a decidedly anticonsequentialist (and,
antiutilitarian) character,
the fourth could appear to embrace consequentialist reasoning.
Defenders of the principle of justice attempt to accommodate the consequentialist
character of the fourth condition while ensuring that it does not render the
more complex features of the principle irrelevant.

Applying the principle of double effect...

Supporters of the
principle of double effect argue that, in situations which a "double effect"
follows from one's conduct and where all four
conditions are met, the conduct under consideration by the agent is ethically
permissible despite the bad result. As a consequence of this line of
reasoning, the principle of double effect has played a significant role in
the discussion of many difficult ethical questions.

The most prominent
applications are found in medical ethics, where the principle figures
prominently in attempts to distinguish among permissible and impermissible
procedures in a range of cases. These include:

Palliative care,
euthanasia, and physician-assisted suicide

Birth control pills

Bioethics,
nonprofessional bioethics, euthanasia, genetics

Should a pain-killing drug be administered to a person suffering intense, unendurable pain? A physician may prescribe and a nurse may administer
doses of morphine that are large enough to ease the pain but will also
hasten death. Conduct aimed at relieving pain is ethically legitimate
in itself because the patient's death was not intended nor was it the means
by which the pain was to be relieved.

Consider the case where a pregnancy may need to be terminated in order to
preserve the life of the mother. The principle of double effect is alleged to allow the
removal of a life-threatening cancerous uterus, even though this procedure
will bring the death of a fetus, on the grounds that in this case the death
of the fetus is not "directly" intended. The principle of
double effect disallows cases,
however, in which a craniotomy (the crushing of the fetus's skull) is
required to preserve a pregnant woman's life, on the grounds that here a
genuine evil, the death of the fetus, is "directly" intended. There is
significant disagreement, even among those ethicists who accept the
principle, about the cogency of this application. Some argue, by emphasizing
the fourth criterion of "proportionality," that the greater value attaching
to the pregnant woman's life makes even craniotomy ethically acceptable.
Other ethicists fail to see a significant difference between the merely
"foreseen" death of the fetus in the cancerous uterus case and the
"directly" intended death in the craniotomy case.

Still other ethicists
argue that the mother's willingness to sacrifice her life for the sake of
her child, as is the case of St.
Gianna Beretta Molla, reflects a character fully grounded in the
philosophical (or "natural") virtue of courage and the theological (or
"cardinal") virtue of love. Consider the application
of the principle of double effect in a similar
case. A pregnant woman bearing a nonviable fetus, for example, may be
found to have a cancerous womb that will cause her death if it is not
excised as soon as possible. The operation of hysterectomy is ethically
lawful, for this operation is permissible in itself as a normal means of
saving the woman's life. She does not positively will the death of her
child, but permits it as an unavoidable evil. Both the benefit to her health
and the death of her child follow from the surgery with equal directness or
immediacy in the order of causality, although the death of the child is
prior in the order of time. The woman's chance of restoration to health (the
good effect) is sufficiently desirable to compensate for the death of the
fetus (the bad effect), which most likely probably not survive even if the
operation were not performed.

However, were the woman
suffering from kidney disease, heart trouble, or tuberculosis, which would
be easier to care for if she were relieved of the pregnancy, it would be
unethical to perform an abortion. The reason? In this case the third
condition for the proper use of the principle of the double effect is lacking. The relief to the woman comes as an effect of the abortion,
not directly as an effect of the surgery. Hence, a bad means would be
employed to produce a good end.

The principle of double
effect can be applied to questions about defending oneself. For
example, St. Thomas may have
visualized this principle it when he argued in the Summa theologiae
(2a2ae, 64.7) that a person may kill an unjust aggressor when this is
necessary to save his own life. That is, a defensive action to
impede an unjust attack upon one's life may also result in the attacker's
death. However, the intention was not to kill the attacker but to stop
the attack. Had the intention to be to kill the attacker, killing the
attacker would be unethical. However, the attacker's death is not the
means by which the individual saved one's life; successfully stopping the
attack is.
One difficulty in the application of the principle of double effect to this
case, however, is that it seems to lack the third condition, since the
preservation of one's own life seems to follow from the killing of the
aggressor. Hence, theologians would argue in this case that God
gives permission to the victim to protect oneself, if necessary, by a direct
slaying of the unjust assailant.

Consider the
following situation which confronted President Harry S. Truman. A nation may launch an air attack on an important military
objective of the enemy even though a comparatively small number of
noncombatants are killed. This evil effect is compensated for by the
great benefit gained through the destruction of the target. This would not
be true, however, if the number of noncombatants slain in the attack were out of
proportion to the benefits gained, as is clear from the fourth condition,
namely, the principle of justice. Furthermore, if the direct purpose of the attack
was to
kill a large number of noncombatants so that the enemy's morale would
be broken down and they would sue for peace, the attack was be unethical because the third condition for the lawful use of the principle
of double effect (the principle of nonmalfeasance) would not be
fulfilled because a nation would be using a bad means to obtain a good
end.

Cases applying the
principle of double effect tend to be stated in the abstract. But, people frequently
apply the principle of
double effect in the ordinary affairs of human life largely unaware of the
principle's four speculative requirements and relying on common sense
instead.

Consider the following
examples of physical evils such as danger to life and bodily welfare that
are ordinarily tolerated because of the good outcome that is envisioned:

an aviator who tests
planes in order to improve aeronautic equipment but may crash and die as a
result;

the doctor who treats
patients affected with contagious diseases and may become infected
himself;

the policeman who
attempts to capture an armed criminal and, in the process, may be killed;

the fireman who
responds to a three-alarm fire and may die as a result of fighting the fire;
and,

the priest who
ministers to lepers and may become leprous himself.

All of these actions are
ethical using the principle of the double effect because the bad effect
that these agents may incur to their own life or health is overweighed by the good
effect their conduct confers upon society.